Triplet Sensitization in an Anionic Poly(phenyleneethynylene) Conjugated Polyelectrolyte by Cationic Iridium Complexes

Abstract

We describe a systematic study of triplet sensitization in a poly(phenyleneethynylene) conjugated polyelectrolyte (CPE) in methanol solution by using a series of three cationic iridium complexes with varying triplet energy. The cationic iridium complexes bind to the anionic CPE by ion-pairing, leading to singlet state quenching of the polymer, and allowing for efficient back-transfer of triplet excitation energy to the polymer. Efficient (amplified quenching) of the polymer's fluorescence is observed for each iridium complex, with Stern-Volmer quenching constants in excess of 10(5) M(-1). Triplet sensitization is confirmed for two of the iridium complexes by monitoring the relative yield of the CPE triplet state by transient absorption spectroscopy. One of the iridium complexes does not sensitize the CPE triplet, and consideration of the energies of the three complexes allows us to bracket the triplet energy of the CPE within the range 1.95-2.26 eV.

Conjugated Polyelectrolyte‐Induced Self‐Assembly of Alkynylplatinum(II) 2,6‐Bis(benzimidazol‐2′‐yl)pyridine Complexes

“…23c–e From the intersection of the electronic absorption and emission spectra of 1 , the E T of 1 is estimated to be 2.24 eV. In the light of earlier investigations on the E T of conjugated polymers,28a, b the triplet state of 1 is sufficiently energetic for the Dexter TEBT from 1 to PPE‐SO 3 − to occur. This is further supported by the nanosecond TA experiments (Figure S9 in the Supporting Information).…”

Supramolecular iridium(III) assemblies

“…Images b) and c) are adapted from Ref. [82] -published by OSA publishing.Schanze and co-workers[83] reported an ion-paired assembly between the anionic poly(phenyleneethynylene) electrolyte (PPESO 3 -) and the cationic Ir(III) complex 4bCl(Figure 2a…”

Enhancing the ROS generation ability of a rhodamine-decorated iridium(iii) complex by ligand regulation for endoplasmic reticulum-targeted photodynamic therapy

“…The lifetime of the excited state involving the iridium(III) metal centre, such as metal-to-ligand charge transfer (MLCT) or metal-perturbed intraligand (IL) charge transfer, was reported to enhance luminescence quantum yield (F lum ). 43 In order to test our strategy, an extended p-conjugated dpqx cyclometallating ligand with a lower-lying intraligand (IL) state was employed in this study. Additionally, the lower excitation and luminescence energies upon variation of this ligand are advantageous for biological applications and compatibility.…”